Hi Vijay,
The Non-persistent objects are not kept in Runtime server, those are completely maintained in Mendix Client side. That means no server side Garbage collection.
Objects will be returned to the client together with the response to a request. Objects created outside the context of a request will automatically be discarded when the event/use of that has finished
refer the below:
https://docs.mendix.com/refguide/transient-objects-garbage-collecting/